Journal of Cardiovascular Nursing
Vol. 31, No. 1, pp 73Y83 x Copyright B 2016 Wolters Kluwer Health, Inc. All rights reserved.
Effects of Massage on Blood Pressure in Patients With Hypertension and Prehypertension A Meta-analysis of Randomized Controlled Trials I-Chen Liao, MSN, RN; Shiah-Lian Chen, PhD; Mei-Yeh Wang, PhD; Pei-Shan Tsai, PhD Background: Massage may help reduce blood pressure; previous studies on the effect of massage on blood pressure have presented conflicting findings. In addition, no systematic review is available. Objective: The aim of this study was to evaluate the evidence concerning the effect of massage on blood pressure in patients with hypertension or prehypertension. Methods: A search was performed on electronic database records up to October 31, 2013, based on the following medical subject headings or keywords: hypertension, massage, chiropractic, manipulation, and blood pressure. The methodological quality of randomized controlled trials was assessed based on the Cochrane collaboration tool. A meta-analysis was performed to evaluate the effect of massage on hypertension. The study selection, data extraction, and validation were performed independently by 2 reviewers. Results: Nine randomized controlled trials met our inclusion criteria. The results of this study show that massage contributes to significantly enhanced reduction in both systolic blood pressure (SBP) (mean difference, j7.39 mm Hg) and diastolic blood pressure (DBP) (mean difference, j5.04 mm Hg) as compared with control treatments in patients with hypertension and prehypertension. The effect size (Hedges g) for SBP and DBP was j0.728 (95% confidence interval, j1.182 to j0.274; P = .002) and j0.334 (95% confidence interval, j0.560 to j0.107; P = .004), respectively. Conclusion: This systematic review found a medium effect of massage on SBP and a small effect on DBP in patients with hypertension or prehypertension. High-quality randomized controlled trials are urgently required to confirm these results, although the findings of this study can be used to guide future research. KEY WORDS:
blood pressure, hypertension, massage, meta-analysis
Background Hypertension is a global problem that typically presents as an asymptomatic, chronic cardiovascular disease.1 However, blood pressure goals are achieved by only 25% to 40% of patients who take antihypertensive I-Chen Liao, MSN, RN Doctoral Student, Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei; and Department of Nursing, College of Medicine and Nursing, Hung Kuang University, Taichung, Taiwan.
Shiah-Lian Chen, PhD Associate Professor, Department of Nursing, National Tai-Chung University of Science and Technology, Taichung, Taiwan.
Mei-Yeh Wang, PhD Associate Professor, Department of Nursing, Cardinal Tien Junior College of Healthcare and Management, New Taipei City, Taiwan.
Pei-Shan Tsai, PhD Professor and Associate Dean, Graduate Institute of Nursing, College of Nursing, Taipei Medical University; and Sleep Science Center, Taipei Medical University Hospital, Taipei, Taiwan. The authors have no conflicts of interest to disclose.
Correspondence Pei-Shan Tsai, PhD, Graduate Institute of Nursing, College of Nursing, Taipei Medical University, 250 Wu-Hsing St, Taipei City, Taiwan 110, ROC ([email protected]). DOI: 10.1097/JCN.0000000000000217
drug treatments.2 Successful treatment of high blood pressure is based on a combination of nonpharmacological and pharmacological therapies.3 Massage therapy is 1 of the most widely accepted complementary and alternative medicine therapies, and it has become a multibilliondollar industry in the United States, with 8.3% of adults receiving at least 1 massage treatment in 2007.4Y6 Although massage therapy can help reduce blood pressure, previous studies have presented conflicting results. A meta-analysis showed that massage therapy can efficiently reduce blood pressure,7 but the effectiveness of massage in managing hypertension remains unclear, as are the optimal type and regimen of massage therapy for lowering blood pressure. Therefore, a meta-analysis on the effects of massage therapy on blood pressure in patients with hypertension and prehypertension was performed in this study.
Methods Data Sources The records of 6 electronic databases were searched from their inception until October 31, 2013. The databases 73
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74 Journal of Cardiovascular Nursing x January/February 2016 examined were the Cochrane Library (Issue 6 of 12, 2013), PubMed, OVID-MEDLINE, CINAHL, Scopus, and EMBASE. Inclusion and Exclusion Criteria Original randomized controlled trials were included in this review based on the following criteria: (1) participantsV studies involving patients with hypertension or prehypertension were included, with no limitations on participant age, sex, or nationality; (2) interventionVresearch where massage therapy was used as an intervention, using either the hands or mechanical devices; (3) comparisonV studies involving specific control interventions were included (ie, use of a placebo, no treatment, standard care, or any active treatment unrelated to massage therapy); and (4) outcomesVstudies were included where the main outcomes of interest involved systolic blood pressure (SBP) and diastolic blood pressure (DBP). Trials were excluded if they were not reported in English. Study Selection Two reviewers independently screened the titles and abstracts of potentially eligible articles by using a predetermined search strategy. Subsequently, the full-text manuscripts of candidate studies were retrieved and reviewed. Finally, 9 studies meeting the inclusion criteria were included in the meta-analysis. Data Extraction Two reviewers extracted data independently according to the following criteria: first author, study year, sample size, blood pressure group (hypertension or prehypertension), sex, mean participant age, experimental and control group intervention, massage type, massage area, treatment dose, follow-up time, and main results. Any discrepancy was discussed until the reviewers reached consensus. Methodological Quality Assessment The methodological quality of randomized controlled trials was assessed independently by the 2 raters based on the Cochrane collaboration tool for assessing risk of bias, using the reporting criteria: low, high, or unclear risk of bias. This tool considers the presence of bias resulting from random sequence generation, allocation concealment, blinding of participants and personnel, incomplete outcome data (because of high discontinuation rates, analysis type, or missing data), selective reporting, and other biases.8 The 2 raters independently assessed the risk of bias; when necessary, consensus was determined with the help of a third rater as the arbitrator. Data Synthesis and Analysis The mean change in outcomes (ie, SBP and DBP) from baseline to posttest was calculated and the differences
between experimental and control groups were estimated. Hedges g and 95% confidence interval (CI) were calculated to determine the effect size. In studies involving multiple control groups, the researchers restricted their analysis to the massage therapy group and a single control group. The I2 statistics and Cochran Q test were used to assess heterogeneity, where an I2 value of 50% or more represented substantial heterogeneity.9 To improve the accuracy of the results, we used a random effect model using variation factors among studies as a correction weight. We performed Egger tests to detect the existence of publication bias among the included studies, with the significance level set at .05.10 Potential publication bias was also examined using a funnel plot. An asymmetric inverted funnel-shape scatter plot of treatment effects against a measure of study size would indicate potential publication bias or the existence of systematic heterogeneity.11 Subgroup analyses according to type of massage, sex, type of control group (active or inactive), whether blinding was involved, treatment sessions, and the massaged area of the body were conducted. Control groups were classified into inactive and active control groups. Inactive controls referred to any condition that was thought to exert no active treatment effect, such as placebo or usual care controls. Active controls were defined as alternative interventions that were believed to exert active treatment effects on the outcome of interest, such as other forms of relaxation treatments. Comprehensive Meta-Analysis Version 2.0 was used to perform the meta-analysis (Biostat Inc, Englewood, New Jersey).
Results Included Studies We identified 144 abstracts from 6 databases. Among these, 18 articles were retrieved and reviewed in full, and a further 9 articles were excluded. Articles were excluded only if they did not meet the inclusion criteria (eg, case report, participants were healthy, not relevant). Thus, 9 randomized controlled trials were considered eligible, all of which were reported in English.12Y20 Figure 1 depicts a summary of the study selection process. Study Characteristics The key data of the 9 included studies are summarized in Table 1. In total, 278 participants were included. The per-group sample size ranged from 8 to 28 participants, and 5 trials12Y16 involved only female participants. The number of massage therapy sessions ranged from 1 to 20, with session durations of 10 to 60 minutes. The total exposure over the study period was 20 to 300 minutes. Five studies involved using Swedish massage therapy,12,13,15,17,18 1 study involved therapeutic chair massage therapy,16 1 study used light-touch and stroking-type
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Effects of Massage on Blood Pressure 75
FIGURE 1. Study selection process.
massage,19 and 2 studies were unclear about the massage type.14,20 The areas massaged were categorized as the whole body, the head, the neck, and back area (including the face, neck, shoulders, upper chest, and back). In terms of control conditions, 4 studies used active control groups16Y18,20 and 5 studies used inactive control groups.12Y15,19 Table 2 shows a summary of the methodological quality of results. We minimized the potential for publication bias by conducting a thorough literature search. The generated funnel plots and Egger test results for the primary outcomes exhibited symmetry and indicated no bias. Effects of Massage Therapy on Blood Pressure The mean change in outcomes (ie, SBP and DBP) from baseline to posttest was calculated, and the differences between experimental and control groups were estimated. One study did report insufficient data for calculating the mean difference.17 The mean difference was thus calculated using the Vernier Caliper by measuring the figure that showed the baseline and posttest data for the massage group and the comparison group. Overall, the pooled results from the 9 studies indicated that massage contributed to a significantly greater reduction in both SBP (mean difference, j7.39 mm Hg)
and DBP (mean difference, j5.04 mm Hg) when compared with the control treatment. As shown in Figure 2A and B, massage therapy had a significant effect on SBP and DBP. The effect size of SBP was j0.728 (95% CI, j1.182 to j0.274; P = .006), and that of DBP was j0.334 (95% CI, j0.560 to j0.107; P = .004). Heterogeneity was observed among the studies for SBP (# 2 = 27.599, df = 8, P = 0.001; I2 = 71%). For DBP, the test for heterogeneity showed homogeneity among studies (# 2 = 5.202, df = 8, P = 0.736; I2 = 0%). Subgroup Analysis: Systolic Blood Pressure Massage therapy significantly improved SBP in patients in the following: (1) 5 studies using Swedish massage therapy; (2) 5 studies that included all-female samples; (3) 4 studies that included both female and male samples; (4) 4 studies that included active control groups; (5) 5 studies that included inactive control groups; (6) 4 studies that blinded outcome assessors; (7) 7 studies involving multiple massage sessions; and (8) 6 studies of massage therapy involving the head, neck, or back. Moderator analysis indicated that the studies that blinded outcome assessors yielded a larger effect size than did those that did not involve blinding (P G .001); studies that used an inactive control group had a significantly larger effect
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Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
9. Hernandez-Reif (2000)
8. Plaugher (2002)
7. Olney (2005)
6. Olney (2008)
5. Jefferson (2010)
4. Moeini (2011)
3. Ju (2013)
2. Givi (2013)
1. Supa’at (2013)
30 subjects Hypertension Male and female Mean age, 51 y
16 subjects Prehypertension and stage I hypertension Women Mean age, 51 y 50 subjects Prehypertensive Women 18Y60 y 55 subjects Hypertensive patients Women Mean age, 53 y 50 subjects Prehypertensive Female 18Y60 y 34 subjects Hypertension Female Mean age, 53 y 29 subjects Prehypertension or controlled hypertension Men and women Mean age, 48 y 14 subjects Hypertension for at least 1 y Men and women Mean age, 54 y 14 subjects Hypertension Men and women Mean age, 37 y
Sample
Massage (unclear type), n = 15 Progressive (muscle relaxation), n = 15
Treatment group (light-touch, stroking-type massage), n = 8 Control group (rested alone), n = 6
Treatment group (Swedish massage), n = 8 Control group (self-determined relaxation method), n = 6
Group 1 (therapeutic chair massage intervention), n = 17 Group 2 (received patient teaching on diaphragmatic breathing), n = 17 Treatment group (Swedish massage), n = 15 Control group (relaxation sessions using learned relaxation techniques), n = 14
Massage (Swedish massage), n = 25 Placebo (relaxed at the same environment with no massage), n = 25
Massage group (unclear type), n = 28 No-treatment control group, n = 27
Massage (Swedish massage), n = 25 Placebo (relaxed at the same environment with no massage), n = 25
Massage (Swedish massage), n = 8 Placebo (rest at the same environment with no massage), n = 8
Intervention
Summary of Controlled Clinical Studies of Massage for Hypertension
First Author (Year)
TABLE 1
Massage Area
Dose
10 min 3 times a week 10 sessions Dose: 100 min
10 min 10 times over 3.5 weeks 10 sessions Dose: 100 min
20 min 1 session Dose: 20 min
10 min 3 times a week 10 sessions Dose: 100 min
10 min 3 times a week 10 sessions Dose: 100 min 60 min 5 sessions in 4 wk Dose: 300 min
60 min once a week 1 session Dose: 60 min
10 min 3 times/week/first month, 2 times/week/ second month 20 sessions Dose: 200 min Whole body, head/arms/torso/legs/back 30 min 2 times a week 10 sessions Dose: 300 min
Localized regions of the spine
Back
Back
Back
Face, neck, shoulders, and upper chest
Whole body, back, posterior legs, anterior legs, abdomen, arms, and shoulders
Face, neck, shoulders, and upper chest
Whole body
Immediate
Immediate
48 h
Immediate
Immediate
Immediate
Immediate
72 h
48 h
Time Point for Posttest
76 Journal of Cardiovascular Nursing x January/February 2016
Effects of Massage on Blood Pressure 77 TABLE 2
Summary of Cochrane’s Risk of Bias
First Author (year) 1. 2. 3. 4. 5. 6. 7. 8. 9.
Supa’at (2013) Givi (2013) Ju (2013) Moeini (2011) Jefferson (2010) Olney (2008) Olney (2005) Plaugher (2002) Hernandez-Reif (2000)
Random Sequence Generation
Allocation Concealment
Blinding of Participants and Personnel
Blinding of Outcome Assessment
Incomplete Outcome Data
Selective Reporting
Other Sources of Bias
V V ? V V V V V V
V V ? V V V V V V
X X V X X X V X V
? V ? V ? ? V V ?
V V V V V V V X X
V V V V V V V X X
V V V V ? V V V V
X = high risk; V = low risk; ? = unclear risk.
size than did those that included an active control group (P = .003). The results are illustrated in Figure 3AYH and summarized in Table 3. Meta-regression revealed that the effect of massage on SBP was not significantly associated with total massage time (P = .058).
Subgroup Analysis: Diastolic Blood Pressure Massage therapy significantly improved DBP in patients in the following: (1) 4 studies that used non-Swedish massage therapy; (2) 4 studies that enrolled both female and male participants in the sample; (3) 4 studies involving
FIGURE 2. Forest plots of the overall effect of massage on hypertension. (A) Systolic. Test for overall effect: Z = 3.142 (P = .002). (B) Diastolic. Test for overall effect: Z = 2.889 (P = .004). SBP indicates systolic blood pressure; DBP, diastolic blood pressure; CI, confidence interval.
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78 Journal of Cardiovascular Nursing x January/February 2016
FIGURE 3. Continues.
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Effects of Massage on Blood Pressure 79
FIGURE 3. Forest plots of the subgroup effect of massage on systolic blood pressure in hypertension. (A) Swedish massage. Test
for overall effect: Z = j2.901 (P = .004). (B) Female. Test for overall effect: Z = j2.291 (P = .022). (C) Female and male. Test for overall effect: Z = j2.499 (P = .049). (D) Active. Test for overall effect: Z = j2.126 (P = .034). (E) Inactive. Test for overall effect: Z = j2.161 (P = .031). (F) Blinding. Test for overall effect: Z = j5.004 (P = .000). (G) Multiple sessions. Test for overall effect: Z = j2.999 (P = .003). (H) Head, neck, or back. Test for overall effect: Z = j3.331 (P = .001). A forest plot is a graphical representation of component studies within a meta-analysis. A horizontal line runs through the square to show its 95% confidence interval. The squares represent point estimates for each study, and the overall estimate from the meta-analysis and its confidence interval are noted at the bottom (represented as a diamond). Each study is marked by a square (placed where the data measure the effect). The size of the each square was proportional to the weight that the individual study contributed to the meta-analysis. SBP indicates systolic blood pressure; DBP, diastolic blood pressure; CI, confidence interval.
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80 Journal of Cardiovascular Nursing x January/February 2016 TABLE 3 Results of Systolic Blood Pressure Subgroup Effect Analyses: Number of Trials per Subgroup, Effect Sizes, Heterogeneity, and Subgroup Differences Subgroup Category
Number of Trials
Effect Size (Confidence Interval)
Heterogeneity
Pa
5 4
j1.051 (j1.761 to j0.341)b j0.320 (j0.655 to 0.015)
I2 = 75% I2 = 0%
.079
5 4
j0.776 (j1.440 to j0.047)b j0.536 (j0.957 to j0.116)b
I2 = 80% I2 = 50%
.809
4 5
j0.605 (j1.163 to j1.103)b j0.779 (j1.486 to j0.073)b
I2 = 50% I2 = 80%
.003a
4 5
j1.382 (j1.923 to j0.841)b j0.269 (j0.569 to 0.032)
I2 = 43% I2 = 0%
G.001a
2 7
j0.331 (j0.872 to 0.209) j0.853 (j1.411 to j0.296)b
I2 = 0% I2 = 75%
.334
3 6
j0.230 (j0.613 to 0.152) j0.988 (j1.570 to j0.407)b
I2 = 0% I2 = 71%
0.080
Type of massage Swedish Non-Swedish Sex Female Female and male Control group Active Inactive Blinding of outcome assessors Yes No Session Single session Multiple sessions Area Whole body Head, neck, or back a
Moderator analyses for subgroup differences. Significant subgroup effects, P G .05.
b
active control groups; (4) 5 studies with blinded outcome assessors; (5) 7 studies reporting multiple treatment sessions; (6) 3 studies that involved whole body massage; and (7) 6 studies that reported head, neck, or back massage therapy. As shown in Table 4, moderator analysis was nonsignificant for all moderators except for the moderating effect of control conditions. Studies that used an active control group reported significantly larger effect sizes than did those involving an inactive control group (P = .011).
Meta-regression results revealed a nonsignificant association between doses and effect size (P = .735).
Discussion Overview of Findings When the results of all 9 studies in this review were pooled, we observed that massage therapy was associated with a significant reduction in SBP and DBP in
TABLE 4
Results of Diastolic Blood Pressure Subgroup Effect Analyses: Number of Trials per Subgroup, Effect Sizes, Heterogeneity, and Subgroup Differences Subgroup Category
Number of Trials
Effect Size (Confidence Interval)
Heterogeneity
Pa
5 4
j0.301 (j0.608 to 0.006) j0.373 (j0.708 to j0.037)b
I2 = 8% I2 = 0%
.759
5 4
j0.240 (j0.510 to 0.030) j0.556 (j0.972 to j0.140)b
I2 = 0% I2 = 0%
.212
4 5
j0.518 (j0.906 to j0.130)b j0.238 (j0.528 to 0.052)
I2 = 0% I2 = 0%
.011a
4 5
j0.177 (j0.538 to 0.183) j0.435 (j0.726 to j0.145)b
I2 = 0% I2 = 0%
.275
2 7
j0.508 (j1.054 to 0.037) j0.297 (j0.546 to j0.049)b
I2 = 0% I2 = 0%
.491
3 6
j0.392 (j0.777 to j0.006)b j0.303 (j0.583 to j0.023)b
I2 = 0% I2 = 0%
.715
Type of massage Swedish Non-Swedish Sex Female Female and male Control group Active Inactive Blind of outcome assessors Yes No Session Single session Multiple sessions Area Whole body Head, neck, or back a
Moderator analyses for subgroup differences Significant subgroup effect, P G .05.
b
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Effects of Massage on Blood Pressure 81
patients with hypertension and prehypertension. Massage therapy contributed to a 7Ymm Hg reduction in SBP and 5Ymm Hg reduction in DBP as compared with control conditions. A recent meta-analysis reported that administering blood pressure-lowering treatment did not contribute to a significant reduction in cardiovascular risk among patients with mild hypertension.21 However, linear associations were observed between blood pressure and angina, myocardial in farction, or subarachnoid hemorrhage.22 Treatments that reduce blood pressure, therefore, can potentially reduce the risk of various cardiovascular diseases. Moreover, a lifetime burden of hypertension has been reported. Compared with participants with normal blood pressure, those with blood pressure equal to or higher than 140/90 mm Hg exhibited increased overall cardiovascular disease at 30 years of age, and they developed cardiovascular disease 5 years earlier.22 A 7Ymm Hg reduction in SBP and 5Ymm Hg reduction in DBP are thus potentially of clinical significance. Subgroup analyses of the type of massage revealed potentially paradoxical findings for SBP and DBP. Swedish massage therapy effectively reduced SBP, whereas nonSwedish massage therapy effectively reduced DBP. Raised SBP is modulated partially by a change in balance of sympathetic activity and parasympathetic activity.23 Swedish massage is known for its therapeutic relaxation effects, and hypertension is associated with stress.12 Swedish massage is classified as a superficial type of massage, consisting of 5 primary stroking actions that stimulate the circulation of blood through the soft tissues of the body.24,25 The significant reduction in heart rate induced by Swedish massage supports the link between enhanced parasympathetic activity and reduced SBP.25 On the other hand, DBP was influenced by peripheral vascular resistance26,27; the mechanical techniques of the Swedish massage may not have direct effect on changes in peripheral vascular resistance. Of note, 2 studies14,20 that we classified as using non-Swedish massage therapy reported inadequately detailed information to determine the exact treatment components. Thus, misclassification of massage type might have occurred. Significant reductions were observed in both SBP and DBP when massage therapy was compared with active control treatments. The superior effect of massage therapy in comparison with active control treatments further supports the notion that massage therapy exerts specific treatment effects in reducing SBP and DBP. Furthermore, our results provide evidence of moderating factors that could influence the effectiveness of treatment effects. For example, massage therapy involving the head, neck, or back was effective in reducing both SBP and DBP. Significant reductions in SBP and DBP were observed for both sexes. Multiple sessions of massage therapy were more effective than 1 session alone. When considering the total exposure of massage (in
minutes) as a continuous variable, the treatment effect was not significantly associated with dose. However, a marginally significant association between the dose and effect size was observed for SBP (P = .058). Further studies are needed to investigate the optimal dose of massage therapy. Previous meta-analyses or systematic reviews have assessed the effect of massage therapy28Y30; however, those reviews were limited in scope, and the participants and outcome measures differed from those discussed in this study. Previous reviews have involved healthy men, hospice patients, postYmyocardial infarction patients, breast cancer patients, or shoulder pain patients. The outcome measures in those studies included pain, anxiety, depression, stress, fatigue, and physiological components of relaxation. Only 1 meta-analysis concluded that applied massage therapy reduced blood pressure; however, the participants reviewed in that study included healthy adults, hypertensive adults, healthy women, patients undergoing cardiac catheterization, and soldiers.7 For SBP, heterogeneity was observed among the reviewed studies. To explore the factors contributing to heterogeneity, we examined whether the type of massage, the sex of participants, control group (active or inactive), quality of studies (blinding of outcome assessors), treatment sessions, and the massaged area of the body affected the effectiveness of the treatment. As expected, moderator analyses revealed that the beneficial effect of massage therapy for SBP was greater for studies involving inactive control groups compared with those that had active control groups, and larger for studies with better quality (blinding assessors). Numerous potentially interesting moderator variables remain unexamined in primary massage therapy research, and only 1 study has determined change in blood pressure and associated factors.31 Systolic blood pressure seemed to decrease after Swedish massage therapy, but the association between changes in blood pressure and the massaged area of the body, duration of the massage, or pressure applied was not statistically significant.31 Previous studies lack a clear definition of the types of massage therapy, and they have a limited number of participants. Unfortunately, the use of different massage therapy techniques by different practitioners may affect the associated therapeutic outcomes. Limitations of the Review Some limitations were encountered while conducting this systematic review. This review may have been affected by the heterogeneity in massage therapy characteristics, including frequency, duration, number of sessions, and massage technique. The number of included studies was small, with each study also having a relatively small sample. Bias was also possible, and
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82 Journal of Cardiovascular Nursing x January/February 2016
What’s New and Important h Massage therapy significantly reduces SBP and DBP compared with control. h Swedish massage therapy causes the largest reduction in SBP in patients with hypertension and prehypertension. h Future studies of higher quality are needed, with a particular emphasis on Swedish massage therapy.
4. 5.
6.
blinding subjects and therapists for treatments is difficult. However, assessor blinding and allocation concealment are critical for reducing bias. Only 4 studies have used blinding in their outcome assessments. Moderator analyses were performed to explain gradients in treatment effect among subgroups. However, because moderator variables cannot be assumed to be statistically independent,32 inferences drawn from these analysis results should be interpreted with caution.
7. 8.
9. 10.
Methodological Recommendations for Future Studies
11.
Future studies considering the mechanism of massage therapy are necessary. To strengthen our evidence, future studies should consider extending this review after the publication of new eligible randomized controlled trials concerning the effect of massage therapy on hypertension. However, future research must include larger samples to increase their explanatory power. In addition, blinding the researcher to the data to prevent possible bias will be critical. Moreover, most studies measured BP immediately before and after massage. Future studies evaluating the intermediate or long-term effects of massage on blood pressure are needed. Finally, future designs should consider the massage type, regimen, massaged area, patient type (prehypertension versus established hypertension), and application of massage therapy for nonpharmacological control of hypertension.
12.
13. 14.
15.
16.
17.
Conclusion Significant differences between the control and massage therapy groups in SBP and DBP were identified, with massage therapy shown to reduce both parameters. Massage therapy is a simple nonpharmacological stress-reduction method that appears to positively impact blood pressure. This review of massage therapy for hypertension provides crucial guidelines for future research.
18.
19.
20.
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Effects of Massage on Blood Pressure 83 23. Biaggioni I. Interventional approaches to reduce sympathetic activity in resistant hypertension: to ablate or stimulate? Hypertension. 2012;59(2):194Y195. 24. Aourell M, Skoog M, Carleson J. Effects of Swedish massage on blood pressure. Complement Ther Clin Pract. 2005; 11(4):242Y246. 25. Cowen VS, Burkett L, Bredimus J. A comparative study of Thai massage and Swedish massage relative to physiological and psychological measures. J Bodyw Mov Ther. 2006;10:266Y275. 26. Pinto E. Blood pressure and ageing. Postgrad Med J. 2007; 83:109Y114. 27. Guo X, Pantoni L, Simoni M, et al. Blood pressure components and changes in relation to white matter lesions: a 32-year prospective population study. Hypertension. 2009;54(1):57Y62.
28. Kong LJ, Zhan HS, Cheng YW, Yuan WA, Chen B, Fang M. Massage therapy for neck and shoulder pain: a systematic review and meta-analysis. Evid Based Complement Alternat Med: eCAM. 2013;2013:613279. 29. Smith JM, Sullivan SJ, Baxter GD. Massage therapy: more than a modality. N Z J Physiother. 2010;38(2):44Y51. 30. Labyak SE, Metzger BL. The effects of effleurage backrub on the physiological components of relaxation: a meta-analysis. Nurs Res. 1997;46(1):59Y62. 31. Cambron JA, Dexheimer J, Coe P. Changes in blood pressure after various forms of therapeutic massage: a preliminary study. J Altern Complement Med. 2006;12:65Y70. 32. Lipsey MW. Those confounded moderators in meta-analysis: good, bad, and ugly. Ann Am Acad Pol Soc Sci. 2003;587:69Y81.
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Vol. 31, No. 1, pp 73Y83 x Copyright B 2016 Wolters Kluwer Health, Inc. All rights reserved.
Effects of Massage on Blood Pressure in Patients With Hypertension and Prehypertension A Meta-analysis of Randomized Controlled Trials I-Chen Liao, MSN, RN; Shiah-Lian Chen, PhD; Mei-Yeh Wang, PhD; Pei-Shan Tsai, PhD Background: Massage may help reduce blood pressure; previous studies on the effect of massage on blood pressure have presented conflicting findings. In addition, no systematic review is available. Objective: The aim of this study was to evaluate the evidence concerning the effect of massage on blood pressure in patients with hypertension or prehypertension. Methods: A search was performed on electronic database records up to October 31, 2013, based on the following medical subject headings or keywords: hypertension, massage, chiropractic, manipulation, and blood pressure. The methodological quality of randomized controlled trials was assessed based on the Cochrane collaboration tool. A meta-analysis was performed to evaluate the effect of massage on hypertension. The study selection, data extraction, and validation were performed independently by 2 reviewers. Results: Nine randomized controlled trials met our inclusion criteria. The results of this study show that massage contributes to significantly enhanced reduction in both systolic blood pressure (SBP) (mean difference, j7.39 mm Hg) and diastolic blood pressure (DBP) (mean difference, j5.04 mm Hg) as compared with control treatments in patients with hypertension and prehypertension. The effect size (Hedges g) for SBP and DBP was j0.728 (95% confidence interval, j1.182 to j0.274; P = .002) and j0.334 (95% confidence interval, j0.560 to j0.107; P = .004), respectively. Conclusion: This systematic review found a medium effect of massage on SBP and a small effect on DBP in patients with hypertension or prehypertension. High-quality randomized controlled trials are urgently required to confirm these results, although the findings of this study can be used to guide future research. KEY WORDS:
blood pressure, hypertension, massage, meta-analysis
Background Hypertension is a global problem that typically presents as an asymptomatic, chronic cardiovascular disease.1 However, blood pressure goals are achieved by only 25% to 40% of patients who take antihypertensive I-Chen Liao, MSN, RN Doctoral Student, Graduate Institute of Nursing, College of Nursing, Taipei Medical University, Taipei; and Department of Nursing, College of Medicine and Nursing, Hung Kuang University, Taichung, Taiwan.
Shiah-Lian Chen, PhD Associate Professor, Department of Nursing, National Tai-Chung University of Science and Technology, Taichung, Taiwan.
Mei-Yeh Wang, PhD Associate Professor, Department of Nursing, Cardinal Tien Junior College of Healthcare and Management, New Taipei City, Taiwan.
Pei-Shan Tsai, PhD Professor and Associate Dean, Graduate Institute of Nursing, College of Nursing, Taipei Medical University; and Sleep Science Center, Taipei Medical University Hospital, Taipei, Taiwan. The authors have no conflicts of interest to disclose.
Correspondence Pei-Shan Tsai, PhD, Graduate Institute of Nursing, College of Nursing, Taipei Medical University, 250 Wu-Hsing St, Taipei City, Taiwan 110, ROC ([email protected]). DOI: 10.1097/JCN.0000000000000217
drug treatments.2 Successful treatment of high blood pressure is based on a combination of nonpharmacological and pharmacological therapies.3 Massage therapy is 1 of the most widely accepted complementary and alternative medicine therapies, and it has become a multibilliondollar industry in the United States, with 8.3% of adults receiving at least 1 massage treatment in 2007.4Y6 Although massage therapy can help reduce blood pressure, previous studies have presented conflicting results. A meta-analysis showed that massage therapy can efficiently reduce blood pressure,7 but the effectiveness of massage in managing hypertension remains unclear, as are the optimal type and regimen of massage therapy for lowering blood pressure. Therefore, a meta-analysis on the effects of massage therapy on blood pressure in patients with hypertension and prehypertension was performed in this study.
Methods Data Sources The records of 6 electronic databases were searched from their inception until October 31, 2013. The databases 73
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74 Journal of Cardiovascular Nursing x January/February 2016 examined were the Cochrane Library (Issue 6 of 12, 2013), PubMed, OVID-MEDLINE, CINAHL, Scopus, and EMBASE. Inclusion and Exclusion Criteria Original randomized controlled trials were included in this review based on the following criteria: (1) participantsV studies involving patients with hypertension or prehypertension were included, with no limitations on participant age, sex, or nationality; (2) interventionVresearch where massage therapy was used as an intervention, using either the hands or mechanical devices; (3) comparisonV studies involving specific control interventions were included (ie, use of a placebo, no treatment, standard care, or any active treatment unrelated to massage therapy); and (4) outcomesVstudies were included where the main outcomes of interest involved systolic blood pressure (SBP) and diastolic blood pressure (DBP). Trials were excluded if they were not reported in English. Study Selection Two reviewers independently screened the titles and abstracts of potentially eligible articles by using a predetermined search strategy. Subsequently, the full-text manuscripts of candidate studies were retrieved and reviewed. Finally, 9 studies meeting the inclusion criteria were included in the meta-analysis. Data Extraction Two reviewers extracted data independently according to the following criteria: first author, study year, sample size, blood pressure group (hypertension or prehypertension), sex, mean participant age, experimental and control group intervention, massage type, massage area, treatment dose, follow-up time, and main results. Any discrepancy was discussed until the reviewers reached consensus. Methodological Quality Assessment The methodological quality of randomized controlled trials was assessed independently by the 2 raters based on the Cochrane collaboration tool for assessing risk of bias, using the reporting criteria: low, high, or unclear risk of bias. This tool considers the presence of bias resulting from random sequence generation, allocation concealment, blinding of participants and personnel, incomplete outcome data (because of high discontinuation rates, analysis type, or missing data), selective reporting, and other biases.8 The 2 raters independently assessed the risk of bias; when necessary, consensus was determined with the help of a third rater as the arbitrator. Data Synthesis and Analysis The mean change in outcomes (ie, SBP and DBP) from baseline to posttest was calculated and the differences
between experimental and control groups were estimated. Hedges g and 95% confidence interval (CI) were calculated to determine the effect size. In studies involving multiple control groups, the researchers restricted their analysis to the massage therapy group and a single control group. The I2 statistics and Cochran Q test were used to assess heterogeneity, where an I2 value of 50% or more represented substantial heterogeneity.9 To improve the accuracy of the results, we used a random effect model using variation factors among studies as a correction weight. We performed Egger tests to detect the existence of publication bias among the included studies, with the significance level set at .05.10 Potential publication bias was also examined using a funnel plot. An asymmetric inverted funnel-shape scatter plot of treatment effects against a measure of study size would indicate potential publication bias or the existence of systematic heterogeneity.11 Subgroup analyses according to type of massage, sex, type of control group (active or inactive), whether blinding was involved, treatment sessions, and the massaged area of the body were conducted. Control groups were classified into inactive and active control groups. Inactive controls referred to any condition that was thought to exert no active treatment effect, such as placebo or usual care controls. Active controls were defined as alternative interventions that were believed to exert active treatment effects on the outcome of interest, such as other forms of relaxation treatments. Comprehensive Meta-Analysis Version 2.0 was used to perform the meta-analysis (Biostat Inc, Englewood, New Jersey).
Results Included Studies We identified 144 abstracts from 6 databases. Among these, 18 articles were retrieved and reviewed in full, and a further 9 articles were excluded. Articles were excluded only if they did not meet the inclusion criteria (eg, case report, participants were healthy, not relevant). Thus, 9 randomized controlled trials were considered eligible, all of which were reported in English.12Y20 Figure 1 depicts a summary of the study selection process. Study Characteristics The key data of the 9 included studies are summarized in Table 1. In total, 278 participants were included. The per-group sample size ranged from 8 to 28 participants, and 5 trials12Y16 involved only female participants. The number of massage therapy sessions ranged from 1 to 20, with session durations of 10 to 60 minutes. The total exposure over the study period was 20 to 300 minutes. Five studies involved using Swedish massage therapy,12,13,15,17,18 1 study involved therapeutic chair massage therapy,16 1 study used light-touch and stroking-type
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Effects of Massage on Blood Pressure 75
FIGURE 1. Study selection process.
massage,19 and 2 studies were unclear about the massage type.14,20 The areas massaged were categorized as the whole body, the head, the neck, and back area (including the face, neck, shoulders, upper chest, and back). In terms of control conditions, 4 studies used active control groups16Y18,20 and 5 studies used inactive control groups.12Y15,19 Table 2 shows a summary of the methodological quality of results. We minimized the potential for publication bias by conducting a thorough literature search. The generated funnel plots and Egger test results for the primary outcomes exhibited symmetry and indicated no bias. Effects of Massage Therapy on Blood Pressure The mean change in outcomes (ie, SBP and DBP) from baseline to posttest was calculated, and the differences between experimental and control groups were estimated. One study did report insufficient data for calculating the mean difference.17 The mean difference was thus calculated using the Vernier Caliper by measuring the figure that showed the baseline and posttest data for the massage group and the comparison group. Overall, the pooled results from the 9 studies indicated that massage contributed to a significantly greater reduction in both SBP (mean difference, j7.39 mm Hg)
and DBP (mean difference, j5.04 mm Hg) when compared with the control treatment. As shown in Figure 2A and B, massage therapy had a significant effect on SBP and DBP. The effect size of SBP was j0.728 (95% CI, j1.182 to j0.274; P = .006), and that of DBP was j0.334 (95% CI, j0.560 to j0.107; P = .004). Heterogeneity was observed among the studies for SBP (# 2 = 27.599, df = 8, P = 0.001; I2 = 71%). For DBP, the test for heterogeneity showed homogeneity among studies (# 2 = 5.202, df = 8, P = 0.736; I2 = 0%). Subgroup Analysis: Systolic Blood Pressure Massage therapy significantly improved SBP in patients in the following: (1) 5 studies using Swedish massage therapy; (2) 5 studies that included all-female samples; (3) 4 studies that included both female and male samples; (4) 4 studies that included active control groups; (5) 5 studies that included inactive control groups; (6) 4 studies that blinded outcome assessors; (7) 7 studies involving multiple massage sessions; and (8) 6 studies of massage therapy involving the head, neck, or back. Moderator analysis indicated that the studies that blinded outcome assessors yielded a larger effect size than did those that did not involve blinding (P G .001); studies that used an inactive control group had a significantly larger effect
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9. Hernandez-Reif (2000)
8. Plaugher (2002)
7. Olney (2005)
6. Olney (2008)
5. Jefferson (2010)
4. Moeini (2011)
3. Ju (2013)
2. Givi (2013)
1. Supa’at (2013)
30 subjects Hypertension Male and female Mean age, 51 y
16 subjects Prehypertension and stage I hypertension Women Mean age, 51 y 50 subjects Prehypertensive Women 18Y60 y 55 subjects Hypertensive patients Women Mean age, 53 y 50 subjects Prehypertensive Female 18Y60 y 34 subjects Hypertension Female Mean age, 53 y 29 subjects Prehypertension or controlled hypertension Men and women Mean age, 48 y 14 subjects Hypertension for at least 1 y Men and women Mean age, 54 y 14 subjects Hypertension Men and women Mean age, 37 y
Sample
Massage (unclear type), n = 15 Progressive (muscle relaxation), n = 15
Treatment group (light-touch, stroking-type massage), n = 8 Control group (rested alone), n = 6
Treatment group (Swedish massage), n = 8 Control group (self-determined relaxation method), n = 6
Group 1 (therapeutic chair massage intervention), n = 17 Group 2 (received patient teaching on diaphragmatic breathing), n = 17 Treatment group (Swedish massage), n = 15 Control group (relaxation sessions using learned relaxation techniques), n = 14
Massage (Swedish massage), n = 25 Placebo (relaxed at the same environment with no massage), n = 25
Massage group (unclear type), n = 28 No-treatment control group, n = 27
Massage (Swedish massage), n = 25 Placebo (relaxed at the same environment with no massage), n = 25
Massage (Swedish massage), n = 8 Placebo (rest at the same environment with no massage), n = 8
Intervention
Summary of Controlled Clinical Studies of Massage for Hypertension
First Author (Year)
TABLE 1
Massage Area
Dose
10 min 3 times a week 10 sessions Dose: 100 min
10 min 10 times over 3.5 weeks 10 sessions Dose: 100 min
20 min 1 session Dose: 20 min
10 min 3 times a week 10 sessions Dose: 100 min
10 min 3 times a week 10 sessions Dose: 100 min 60 min 5 sessions in 4 wk Dose: 300 min
60 min once a week 1 session Dose: 60 min
10 min 3 times/week/first month, 2 times/week/ second month 20 sessions Dose: 200 min Whole body, head/arms/torso/legs/back 30 min 2 times a week 10 sessions Dose: 300 min
Localized regions of the spine
Back
Back
Back
Face, neck, shoulders, and upper chest
Whole body, back, posterior legs, anterior legs, abdomen, arms, and shoulders
Face, neck, shoulders, and upper chest
Whole body
Immediate
Immediate
48 h
Immediate
Immediate
Immediate
Immediate
72 h
48 h
Time Point for Posttest
76 Journal of Cardiovascular Nursing x January/February 2016
Effects of Massage on Blood Pressure 77 TABLE 2
Summary of Cochrane’s Risk of Bias
First Author (year) 1. 2. 3. 4. 5. 6. 7. 8. 9.
Supa’at (2013) Givi (2013) Ju (2013) Moeini (2011) Jefferson (2010) Olney (2008) Olney (2005) Plaugher (2002) Hernandez-Reif (2000)
Random Sequence Generation
Allocation Concealment
Blinding of Participants and Personnel
Blinding of Outcome Assessment
Incomplete Outcome Data
Selective Reporting
Other Sources of Bias
V V ? V V V V V V
V V ? V V V V V V
X X V X X X V X V
? V ? V ? ? V V ?
V V V V V V V X X
V V V V V V V X X
V V V V ? V V V V
X = high risk; V = low risk; ? = unclear risk.
size than did those that included an active control group (P = .003). The results are illustrated in Figure 3AYH and summarized in Table 3. Meta-regression revealed that the effect of massage on SBP was not significantly associated with total massage time (P = .058).
Subgroup Analysis: Diastolic Blood Pressure Massage therapy significantly improved DBP in patients in the following: (1) 4 studies that used non-Swedish massage therapy; (2) 4 studies that enrolled both female and male participants in the sample; (3) 4 studies involving
FIGURE 2. Forest plots of the overall effect of massage on hypertension. (A) Systolic. Test for overall effect: Z = 3.142 (P = .002). (B) Diastolic. Test for overall effect: Z = 2.889 (P = .004). SBP indicates systolic blood pressure; DBP, diastolic blood pressure; CI, confidence interval.
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78 Journal of Cardiovascular Nursing x January/February 2016
FIGURE 3. Continues.
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Effects of Massage on Blood Pressure 79
FIGURE 3. Forest plots of the subgroup effect of massage on systolic blood pressure in hypertension. (A) Swedish massage. Test
for overall effect: Z = j2.901 (P = .004). (B) Female. Test for overall effect: Z = j2.291 (P = .022). (C) Female and male. Test for overall effect: Z = j2.499 (P = .049). (D) Active. Test for overall effect: Z = j2.126 (P = .034). (E) Inactive. Test for overall effect: Z = j2.161 (P = .031). (F) Blinding. Test for overall effect: Z = j5.004 (P = .000). (G) Multiple sessions. Test for overall effect: Z = j2.999 (P = .003). (H) Head, neck, or back. Test for overall effect: Z = j3.331 (P = .001). A forest plot is a graphical representation of component studies within a meta-analysis. A horizontal line runs through the square to show its 95% confidence interval. The squares represent point estimates for each study, and the overall estimate from the meta-analysis and its confidence interval are noted at the bottom (represented as a diamond). Each study is marked by a square (placed where the data measure the effect). The size of the each square was proportional to the weight that the individual study contributed to the meta-analysis. SBP indicates systolic blood pressure; DBP, diastolic blood pressure; CI, confidence interval.
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80 Journal of Cardiovascular Nursing x January/February 2016 TABLE 3 Results of Systolic Blood Pressure Subgroup Effect Analyses: Number of Trials per Subgroup, Effect Sizes, Heterogeneity, and Subgroup Differences Subgroup Category
Number of Trials
Effect Size (Confidence Interval)
Heterogeneity
Pa
5 4
j1.051 (j1.761 to j0.341)b j0.320 (j0.655 to 0.015)
I2 = 75% I2 = 0%
.079
5 4
j0.776 (j1.440 to j0.047)b j0.536 (j0.957 to j0.116)b
I2 = 80% I2 = 50%
.809
4 5
j0.605 (j1.163 to j1.103)b j0.779 (j1.486 to j0.073)b
I2 = 50% I2 = 80%
.003a
4 5
j1.382 (j1.923 to j0.841)b j0.269 (j0.569 to 0.032)
I2 = 43% I2 = 0%
G.001a
2 7
j0.331 (j0.872 to 0.209) j0.853 (j1.411 to j0.296)b
I2 = 0% I2 = 75%
.334
3 6
j0.230 (j0.613 to 0.152) j0.988 (j1.570 to j0.407)b
I2 = 0% I2 = 71%
0.080
Type of massage Swedish Non-Swedish Sex Female Female and male Control group Active Inactive Blinding of outcome assessors Yes No Session Single session Multiple sessions Area Whole body Head, neck, or back a
Moderator analyses for subgroup differences. Significant subgroup effects, P G .05.
b
active control groups; (4) 5 studies with blinded outcome assessors; (5) 7 studies reporting multiple treatment sessions; (6) 3 studies that involved whole body massage; and (7) 6 studies that reported head, neck, or back massage therapy. As shown in Table 4, moderator analysis was nonsignificant for all moderators except for the moderating effect of control conditions. Studies that used an active control group reported significantly larger effect sizes than did those involving an inactive control group (P = .011).
Meta-regression results revealed a nonsignificant association between doses and effect size (P = .735).
Discussion Overview of Findings When the results of all 9 studies in this review were pooled, we observed that massage therapy was associated with a significant reduction in SBP and DBP in
TABLE 4
Results of Diastolic Blood Pressure Subgroup Effect Analyses: Number of Trials per Subgroup, Effect Sizes, Heterogeneity, and Subgroup Differences Subgroup Category
Number of Trials
Effect Size (Confidence Interval)
Heterogeneity
Pa
5 4
j0.301 (j0.608 to 0.006) j0.373 (j0.708 to j0.037)b
I2 = 8% I2 = 0%
.759
5 4
j0.240 (j0.510 to 0.030) j0.556 (j0.972 to j0.140)b
I2 = 0% I2 = 0%
.212
4 5
j0.518 (j0.906 to j0.130)b j0.238 (j0.528 to 0.052)
I2 = 0% I2 = 0%
.011a
4 5
j0.177 (j0.538 to 0.183) j0.435 (j0.726 to j0.145)b
I2 = 0% I2 = 0%
.275
2 7
j0.508 (j1.054 to 0.037) j0.297 (j0.546 to j0.049)b
I2 = 0% I2 = 0%
.491
3 6
j0.392 (j0.777 to j0.006)b j0.303 (j0.583 to j0.023)b
I2 = 0% I2 = 0%
.715
Type of massage Swedish Non-Swedish Sex Female Female and male Control group Active Inactive Blind of outcome assessors Yes No Session Single session Multiple sessions Area Whole body Head, neck, or back a
Moderator analyses for subgroup differences Significant subgroup effect, P G .05.
b
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Effects of Massage on Blood Pressure 81
patients with hypertension and prehypertension. Massage therapy contributed to a 7Ymm Hg reduction in SBP and 5Ymm Hg reduction in DBP as compared with control conditions. A recent meta-analysis reported that administering blood pressure-lowering treatment did not contribute to a significant reduction in cardiovascular risk among patients with mild hypertension.21 However, linear associations were observed between blood pressure and angina, myocardial in farction, or subarachnoid hemorrhage.22 Treatments that reduce blood pressure, therefore, can potentially reduce the risk of various cardiovascular diseases. Moreover, a lifetime burden of hypertension has been reported. Compared with participants with normal blood pressure, those with blood pressure equal to or higher than 140/90 mm Hg exhibited increased overall cardiovascular disease at 30 years of age, and they developed cardiovascular disease 5 years earlier.22 A 7Ymm Hg reduction in SBP and 5Ymm Hg reduction in DBP are thus potentially of clinical significance. Subgroup analyses of the type of massage revealed potentially paradoxical findings for SBP and DBP. Swedish massage therapy effectively reduced SBP, whereas nonSwedish massage therapy effectively reduced DBP. Raised SBP is modulated partially by a change in balance of sympathetic activity and parasympathetic activity.23 Swedish massage is known for its therapeutic relaxation effects, and hypertension is associated with stress.12 Swedish massage is classified as a superficial type of massage, consisting of 5 primary stroking actions that stimulate the circulation of blood through the soft tissues of the body.24,25 The significant reduction in heart rate induced by Swedish massage supports the link between enhanced parasympathetic activity and reduced SBP.25 On the other hand, DBP was influenced by peripheral vascular resistance26,27; the mechanical techniques of the Swedish massage may not have direct effect on changes in peripheral vascular resistance. Of note, 2 studies14,20 that we classified as using non-Swedish massage therapy reported inadequately detailed information to determine the exact treatment components. Thus, misclassification of massage type might have occurred. Significant reductions were observed in both SBP and DBP when massage therapy was compared with active control treatments. The superior effect of massage therapy in comparison with active control treatments further supports the notion that massage therapy exerts specific treatment effects in reducing SBP and DBP. Furthermore, our results provide evidence of moderating factors that could influence the effectiveness of treatment effects. For example, massage therapy involving the head, neck, or back was effective in reducing both SBP and DBP. Significant reductions in SBP and DBP were observed for both sexes. Multiple sessions of massage therapy were more effective than 1 session alone. When considering the total exposure of massage (in
minutes) as a continuous variable, the treatment effect was not significantly associated with dose. However, a marginally significant association between the dose and effect size was observed for SBP (P = .058). Further studies are needed to investigate the optimal dose of massage therapy. Previous meta-analyses or systematic reviews have assessed the effect of massage therapy28Y30; however, those reviews were limited in scope, and the participants and outcome measures differed from those discussed in this study. Previous reviews have involved healthy men, hospice patients, postYmyocardial infarction patients, breast cancer patients, or shoulder pain patients. The outcome measures in those studies included pain, anxiety, depression, stress, fatigue, and physiological components of relaxation. Only 1 meta-analysis concluded that applied massage therapy reduced blood pressure; however, the participants reviewed in that study included healthy adults, hypertensive adults, healthy women, patients undergoing cardiac catheterization, and soldiers.7 For SBP, heterogeneity was observed among the reviewed studies. To explore the factors contributing to heterogeneity, we examined whether the type of massage, the sex of participants, control group (active or inactive), quality of studies (blinding of outcome assessors), treatment sessions, and the massaged area of the body affected the effectiveness of the treatment. As expected, moderator analyses revealed that the beneficial effect of massage therapy for SBP was greater for studies involving inactive control groups compared with those that had active control groups, and larger for studies with better quality (blinding assessors). Numerous potentially interesting moderator variables remain unexamined in primary massage therapy research, and only 1 study has determined change in blood pressure and associated factors.31 Systolic blood pressure seemed to decrease after Swedish massage therapy, but the association between changes in blood pressure and the massaged area of the body, duration of the massage, or pressure applied was not statistically significant.31 Previous studies lack a clear definition of the types of massage therapy, and they have a limited number of participants. Unfortunately, the use of different massage therapy techniques by different practitioners may affect the associated therapeutic outcomes. Limitations of the Review Some limitations were encountered while conducting this systematic review. This review may have been affected by the heterogeneity in massage therapy characteristics, including frequency, duration, number of sessions, and massage technique. The number of included studies was small, with each study also having a relatively small sample. Bias was also possible, and
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82 Journal of Cardiovascular Nursing x January/February 2016
What’s New and Important h Massage therapy significantly reduces SBP and DBP compared with control. h Swedish massage therapy causes the largest reduction in SBP in patients with hypertension and prehypertension. h Future studies of higher quality are needed, with a particular emphasis on Swedish massage therapy.
4. 5.
6.
blinding subjects and therapists for treatments is difficult. However, assessor blinding and allocation concealment are critical for reducing bias. Only 4 studies have used blinding in their outcome assessments. Moderator analyses were performed to explain gradients in treatment effect among subgroups. However, because moderator variables cannot be assumed to be statistically independent,32 inferences drawn from these analysis results should be interpreted with caution.
7. 8.
9. 10.
Methodological Recommendations for Future Studies
11.
Future studies considering the mechanism of massage therapy are necessary. To strengthen our evidence, future studies should consider extending this review after the publication of new eligible randomized controlled trials concerning the effect of massage therapy on hypertension. However, future research must include larger samples to increase their explanatory power. In addition, blinding the researcher to the data to prevent possible bias will be critical. Moreover, most studies measured BP immediately before and after massage. Future studies evaluating the intermediate or long-term effects of massage on blood pressure are needed. Finally, future designs should consider the massage type, regimen, massaged area, patient type (prehypertension versus established hypertension), and application of massage therapy for nonpharmacological control of hypertension.
12.
13. 14.
15.
16.
17.
Conclusion Significant differences between the control and massage therapy groups in SBP and DBP were identified, with massage therapy shown to reduce both parameters. Massage therapy is a simple nonpharmacological stress-reduction method that appears to positively impact blood pressure. This review of massage therapy for hypertension provides crucial guidelines for future research.
18.
19.
20.
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